Intertidal marsh as a source of dissolved inorganic carbon and a sink of nitrate in the Satilla River-estuarine complex in the southeastern US

Total dissolved inorganic carbon (DIC), total alkalinity (TA), pH, and nitr ate + nitrite (NOx) data collected during the summer of 1996 in the Satilla River estuary in the southeastern U.S. were used to assess fluxes of DIC a nd NOx between intertidal marshes and estuarine waters and to model system NOx dynamics. Nitrate and nitrite are produced in the low-salinity portion of the estuary. The intertidal marshes are sites of intensive respiration t hat export DIC to the estuary and remove NOx. An integrated view is present ed on the nitrification and denitrification processes in the marsh/estuarin e complex and their relationship to CO2 generation rates. The distribution of NOx in the marsh and estuarine waters indicates that all NOx generated i n the marsh-estuary system is removed in the intertidal marshes, most likel y via denitrification. Model analysis of NOx and river flow data for three seasons indicates that NOx distribution in the estuarine water is also dete rmined by river flow rates. Export fluxes of NOx to the coastal ocean are i nsignificant in all seasons when compared to NOx production rates in the en tire system; however, they are significantly higher than NOx inputs from th e river end member in October 1996. Although only a small fraction (similar to 10%) of DIC generated in the marshes is exported to the coastal sea and around 90% is lost to the atmosphere, it represents a nearly threefold inc rease in riverine DIC flux to the ocean.